Curing

[Logoman]

Does ink need to reach a certain temp (325) or maintain temp for a period of time to cure on the shirt?

[alan802]

Plastisol or waterbased?

[Screened Gear]

Does ink need to reach a certain temp (325) or maintain temp for a period of time to cure on the shirt?

That is a scary question. The truth is no. The ink needs to cure. Hitting a temp or staying at a temp does not guarantee a full cure.

Ok now that I didn't answer your question I will explain what I do. I know my ink deposits and I know the thickest deposit I do is a PFP of white. That ink deposit will take once though my dryer at settings that I have tested and washed a number of times. At those settings the shirt comes out of the dryer at 300 to 310. Now before everyone jumps on me. Let me explain. I don't measure my temp inside the dryer when I am running jobs. I already did that testing and I know when the temp is right in the dryer that the shirts come out and past the dryer gates about 5 inches have a temp of 300 to 310. Doing it this way you don't have as much variables. I have a quartz dryer so the elements pulse on and off. Depending on if they are on or off the temp will change. Also opening the gate will effect the temp. Lastly its just easier to take a temp out side the dryer when your running 250 to 500 shirts. It has worked for me for over 3 years doing it this way. Keep in mind you have to know your ink deposits and dryer settings. If you print a bullet proof white it will take longer then a white shirt with black ink. I do cook my shirts higher and longer then needed but not so much that they scorch or over cook the inks. (you have to do testing on that also.) I have never got a shirt to catch on fire but I have tried to do that with my dryer. It did come out brown.

[Logoman]

Plastisol

[mimosatexas]

I am pretty much certain that the entirety of the ink deposit has to reach a minimum temperature for the proper reaction to happen to "cure" the ink.  That temperature will depend a lot on the type or ink (standard plastisol vs poly plastisol), and different brands and even colors absorb heat differently.  The thickness of the ink deposit will obviously affect the time it takes for everything to reach the proper temperature as well.  Our exit temp is almost always 330-340 read with a laser temp gun a few inches inside the chamber, but that means very little when all the other variables are added in...

[tonypep]

Correct. Metallics reflect heat for instance. I prefer the donut probe as it shows exactly whats going on during the cure and can identify "cold spots" in the dryer.

[blue moon]

the whole ink deposit has to reach the specified temp which in some cases means it has to be held at a certain temp for longer than an instant.  At least, this is what I've been told . . .

pierre

[Frog]

QMC used to list a dwell time, but, it was admitted that in and of itself, that was just to help ensure that the entire film thickness reached cure temp(which can vary from 290-320 with different inks)
Not considered especially accurate, but the paper tape thermometers placed on the inside of the garment on the image area are on the right track.
Similarly, the wire sensors of donut probes, embedded in the bottom of the plastisol layer are considered the most accurate.

In the end, a few trips through the laundry are the ultimate test.

[Screened Gear]

In the end, a few trips through the laundry are the ultimate test.

That is really the only way to test. Heat guns, tapes and donuts are only to measure the temp. A wash test is how your customer will find out that it was undercured. I don't care if the Screen Printing God Himself said 325 for 2 mins on my dryer will cure shirts. I will still wash the shirts many many times to make sure I don't have a customer come in with a undercured job. You dry shirts at a time and temp you think is right. I say time because you have to cook them. I don't agree with when the shirts hit a temp they are cured. I will always say time and temp. They need time. Test with a few washes. Then make changes to your dryer and test again. Keep in mind any air flow into the dryer will change cure time temps needed. An open bay door could kill your cure times. The amount of shirts in the dryer (especially with waterbase) will also effect your dry times and temps. I said it already I over cook my shirts to make sure all of these variables will not drop my dryers efficiency below a full cure for my ink deposits.

You want that ink to be cured. The last thing you want is to reprint a bunch of shirts or lose a customer with a mistake like that.

I am surprised no one said anything about the pull test.

[mimosatexas]

time is irrelevant chemically though, as time is just a means to an end: every molecule of ink reaching the proper temperature.  Once the ink has cured it has cured and keeping at that heat longer does nothing once the reaction has happened.  There are specially formulated transfer inks out there than will regel above a certain temp, but again, temperature is the key, not time.

[Screened Gear]

time is irrelevant chemically though, as time is just a means to an end: every molecule of ink reaching the proper temperature.  Once the ink has cured it has cured and keeping at that heat longer does nothing once the reaction has happened.  There are specially formulated transfer inks out there than will regel above a certain temp, but again, temperature is the key, not time.

What you said is correct but has only to do with how the chemicals in the ink cures. It has nothing to do with setting a dryer so you get a full cure. When you set a dryer you want the temp in the dryer hot enough to cure the ink. The part you miss is the full thickness of the ink needs to reach that magical temp to cure. I could hit the ink with 700 degrees and the top of the ink would cure instantly but the core of that ink will take time to cure.  Flashing ink takes high temp and just enough time to gel the top layer. It takes time to cure. That is the temp and time that I am talking about. Its like BBQing low and slow the meat is not done until the center of the meat is 160 degrees. The out side of the prize cut of brisket was at 160 degrees hours before the center. You need to cook the ink all the way though.

[Colin]

Bottom Line:

ENTIRE INK LAYER must reach fusion temperature.  If fusion happens at 300 degrees, then it must reach 300 degrees THROUGH THE ENTIRE LAYER.



Side note:

The longer an ink is at fusion temperature, THE STRONGER IT'S ADHESION WILL BE.  This only applies to a certain length of time at fusion temp.  That length of time varies between manufacturers.  Too long at fusion temp and the ink will begin to yellow and discolor due to the heat.

[Screened Gear]

Bottom Line:

ENTIRE INK LAYER must reach fusion temperature.  If fusion happens at 300 degrees, then it must reach 300 degrees THROUGH THE ENTIRE LAYER.



Side note:

The longer an ink is at fusion temperature, THE STRONGER IT'S ADHESION WILL BE.  This only applies to a certain length of time at fusion temp.  That length of time varies between manufacturers.  Too long at fusion temp and the ink will begin to yellow and discolor due to the heat.

This is true. But that cured to yellowing window is very large. I have never seen the yellowing but have blistered/boiled a few prints with old dryers that I had. For someone asking about cure temperature I would rather teach them to be at the higher end then how to just reach cure temp. I have never heard of a customer bring a job back that was over cured.

[mimosatexas]

Not to argue, but i mentioned the entire ink layer getting to temp in both posts, not just the surface.  My only real point was it always bugs me when people say "such and such ink requires 2 minutes at 330 to cure" or something similar.  The 2 minutes is not important in and of itself, and is simply a function of the variables that determine if the entirety of the ink has reached the right temperature.  On a warm day with a thin ink deposit it could take 30 seconds, or it could take 10 minutes with HD inks on a cold day with a poorly insulated dryer.

[Screened Gear]

Not to argue, but i mentioned the entire ink layer getting to temp in both posts, not just the surface.  My only real point was it always bugs me when people say "such and such ink requires 2 minutes at 330 to cure" or something similar.  The 2 minutes is not important in and of itself, and is simply a function of the variables that determine if the entirety of the ink has reached the right temperature.  On a warm day with a thin ink deposit it could take 30 seconds, or it could take 10 minutes with HD inks on a cold day with a poorly insulated dryer.

So you don't want to argue...well you got one now, buddy!!!

I am just messing with you. You did say entire ink deposit. You were right. But no one starting out knows what it takes to cure the entire ink deposit. What it takes to cure the entire ink deposit is a temp for a length of time. I never said what temp or for how long. The temp and time is all dependent on variables. When people are start out they ask How do I know the ink is cured. The short answer people say is ink needs to get to 320 degrees. So they take the temp gun and point it at the ink and if it hits 320 they sell those shirts. A week later the customer calls and tells them the ink is falling off the shirts. I was just trying to explain it so the new guy gets it.